TWINS
Encyclopedia
Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) are a pair of NASA
instruments aboard two United States
National Reconnaissance Office
satellite
s in Molniya orbit
s. TWINS was designed to provide stereo images of the Earth's ring current
. The first instrument, TWINS-1, was launched aboard USA-184 on 28 June 2006. TWINS-2 followed aboard USA-200 on March 13, 2008.
Each instrument consists of an energetic neutral atom
imager and a Lyman alpha detector. The ENA imager provides indirect remote sensing of the ring current ions, and the Lyman alpha detector gives a measure of the neutral hydrogen cloud about the Earth, known as the geocorona
. The TWINS prime mission lasted two years, from 2008 to 2010, and has been followed by an extended mission which is ongoing.
spacecraft, TWINS conduct stereoscopic imaging of Earth's magnetosphere
. By imaging the charge exchange neutral atoms over a broad energy range (~1-100 keV) using two identical instruments on two widely spaced high-altitude, high-inclination spacecraft, TWINS enables the 3-dimensional visualization and the resolution of large scale structures and dynamics within the magnetosphere for the first time. In contrast to traditional space experiments, which make measurements at only one point in space, imaging experiments provide simultaneous viewing of different regions of the magnetosphere. Stereo imaging, as done by TWINS, takes the next step of producing 3-D images, and provides a leap ahead in our understanding of the global aspects of the terrestrial magnetosphere.
The ENA imagers observe energetic neutrals produced from the global magnetospheric ion population, over an energy range of 1 to 100 keV with high angular (4-degree) and time (about 1-minute) resolution. A Lyman-alpha geocoronal imager is used to monitor cold exospheric hydrogen atoms that produce ENAs from ions via charge exchange. Complementing these imagers are detectors that measure the local charged particle environment around the spacecraft.
The offset in the orbital phases (apogees at different times) of TWINS 1 and TWINS 2 means that in addition to stereo ENA imaging for several hours twice per day, the two TWINS instruments also obtain essentially continuous magnetospheric observations.
The TWINS instrumentation is essentially the same as the MENA instrument on the IMAGE
spacecraft. This instrumentation consists of a neutral atom imager covering the ~1-100 keV energy range with 4°x4° angular resolution and 1-minute time resolution, and a simple Lyman-alpha imager to monitor the geocorona.
TWINS provides stereo imaging of the Earth's magnetosphere
, the region surrounding the planet controlled by its magnetic field and containing the Van Allen radiation belts and other energetic charged particles. TWINS enables three-dimensional global visualization of this region, leading to greatly enhanced understanding of the connections between different regions of the magnetosphere and their relation to the solar wind.
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
instruments aboard two United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
National Reconnaissance Office
National Reconnaissance Office
The National Reconnaissance Office , located in Chantilly, Virginia, is one of the 16 U.S. intelligence agencies. It designs, builds, and operates the spy satellites of the United States government.-Mission:...
satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s in Molniya orbit
Molniya orbit
Molniya orbit is a type of highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of -90 degree and an orbital period of one half of a sidereal day...
s. TWINS was designed to provide stereo images of the Earth's ring current
Ring current
A ring current is an electric current carried by charged particles trapped in a planet's magnetosphere. It is caused by the longitudinal drift of energetic particles.-Earth's ring current:...
. The first instrument, TWINS-1, was launched aboard USA-184 on 28 June 2006. TWINS-2 followed aboard USA-200 on March 13, 2008.
Each instrument consists of an energetic neutral atom
Energetic neutral atom
Energetic neutral atom imaging, often described as "seeing with atoms", is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and at the boundary of the heliosphere - the far flung outer edge of the solar system.ENA images are constructed...
imager and a Lyman alpha detector. The ENA imager provides indirect remote sensing of the ring current ions, and the Lyman alpha detector gives a measure of the neutral hydrogen cloud about the Earth, known as the geocorona
Geocorona
The geocorona is the luminous part of the outermost region of the Earth's atmosphere, the exosphere. It is seen primarily via far-ultraviolet light from the Sun that is scattered from neutral hydrogen. It extends to at least 15.5 Earth radii...
. The TWINS prime mission lasted two years, from 2008 to 2010, and has been followed by an extended mission which is ongoing.
Mission
Launched as missions of opportunity aboard NRO Improved TrumpetTrumpet (satellite)
TRUMPET , called Advanced Jumpseat by some observers, is reportedly a codename for a series of ELINT reconnaissance satellites launched by the United States during the 1990s to replace the Jumpseat satellites...
spacecraft, TWINS conduct stereoscopic imaging of Earth's magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
. By imaging the charge exchange neutral atoms over a broad energy range (~1-100 keV) using two identical instruments on two widely spaced high-altitude, high-inclination spacecraft, TWINS enables the 3-dimensional visualization and the resolution of large scale structures and dynamics within the magnetosphere for the first time. In contrast to traditional space experiments, which make measurements at only one point in space, imaging experiments provide simultaneous viewing of different regions of the magnetosphere. Stereo imaging, as done by TWINS, takes the next step of producing 3-D images, and provides a leap ahead in our understanding of the global aspects of the terrestrial magnetosphere.
The ENA imagers observe energetic neutrals produced from the global magnetospheric ion population, over an energy range of 1 to 100 keV with high angular (4-degree) and time (about 1-minute) resolution. A Lyman-alpha geocoronal imager is used to monitor cold exospheric hydrogen atoms that produce ENAs from ions via charge exchange. Complementing these imagers are detectors that measure the local charged particle environment around the spacecraft.
The offset in the orbital phases (apogees at different times) of TWINS 1 and TWINS 2 means that in addition to stereo ENA imaging for several hours twice per day, the two TWINS instruments also obtain essentially continuous magnetospheric observations.
The TWINS instrumentation is essentially the same as the MENA instrument on the IMAGE
IMAGE
IMAGE , or Explorer 78, was a NASA MIDEX mission that studied the global response of the Earth's magnetosphere to changes in the solar wind...
spacecraft. This instrumentation consists of a neutral atom imager covering the ~1-100 keV energy range with 4°x4° angular resolution and 1-minute time resolution, and a simple Lyman-alpha imager to monitor the geocorona.
TWINS provides stereo imaging of the Earth's magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
, the region surrounding the planet controlled by its magnetic field and containing the Van Allen radiation belts and other energetic charged particles. TWINS enables three-dimensional global visualization of this region, leading to greatly enhanced understanding of the connections between different regions of the magnetosphere and their relation to the solar wind.
Operation
Routine stereo imaging by TWINS began on 15 June 2008, during an extremely weak geomagnetic storm whose Dst index never fell below -40 nT, as compared to a nominal Dst of -100 nT for classification as a storm. During the TWINS prime mission (2008-2010), an extended and unprecendented solar minimum (from solar cycle 23) prevailed, bringing with it very calm magnetospheric conditions ranging from dead quiet to mildly disturbed. During this time period TWINS observed numerous weak storms, roughly once every 27 days (corresponding to the solar rotation eriod and triggered b solar corotating interaction regions (CIRs). The strongest storm (which was still very mild) observed by TWINS during its prime mission was on 22 July 2009, with Dst reaching a moderate -79 nT. Throughout these extended quiet conditions TWINS images contained ENA signals from both high-altitude (ring current) and low-altitude emission (LAE) regions.Instruments
| Name | Launch name | Spacecraft | Launch date (UTC) | Launch site | Rocket | Orbit | Remarks |
|---|---|---|---|---|---|---|---|
| TWINS-1 | TWINS-A | USA-184 | 28 June 2006 03:30:00 |
VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command .... SLC-6 Vandenberg AFB Space Launch Complex 6 Space Launch Complex-6 at Vandenberg Air Force Base in California is a launch pad and support area. It was originally designed for the launching of the Titan III in support of the cancelled Manned Orbiting Laboratory, and was later rebuilt for the Space Shuttle, which also never used it due to... |
Delta IV-M+(4,2) | 1,138 km x 39,210 km x63.2° | |
| TWINS-2 | TWINS-B | USA-200 | 13 March 2008 10:02 |
VAFB Vandenberg Air Force Base Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command .... SLC-3E Vandenberg AFB Space Launch Complex 3 Space Launch Complex 3 is a launch site at Vandenberg Air Force Base that has been used by Atlas and Thor rockets. It was built in the early 1960s and consists of two pads, SLC-3E and SLC-3W . The East-West coastline at Vandenberg allows SLC-3 to launch over-ocean polar trajectories that avoid... |
Atlas V Atlas V Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance... 411 |
1,652 km x 38,702 km x63.4° |
See also
- STEREOSTEREOSTEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
Two spacecraft launched into heliocentric orbit in 2006 to provide stereographic imagery of the sun.